PHYSICAL AXD CLIMATIC SETTING 17 



down to freezing or only a few degrees above it, 

 merely means that the waters of the lakes have yielded 

 np their heat chiefly to the covering atmosphere, thus 

 delaying the time of killing frosts and winter's cold. 

 If Michigan were inclosed by areas of land instead of 

 water, this process of heat radiation from earth to 

 atmosphere would take place more rapidly and, in 

 the northern districts of the State, early September 

 would find the season of growth for crops brought 

 definitely to an end. 



A chart prepared by the United States Weather 

 Bureau's Grand Eapids office, based on observations 

 covering a period of twenty-five years, brings out 

 very graphically the effect of the Lakes in retarding 

 autumnal frosts. In the minds of most persons, 

 the country adjacent to Lake Superior is sufficiently 

 remote to suggest a subarctic flora and fauna with 

 native Eskimos dining on whale-blubber as dwellers 

 by its shores. Yet in areas projecting into the Lake, 

 such as the Keweenaw Peninsula and White Fish 

 point, as this chart reveals, the first killing frost 

 normally appears about October 10. The most south- 

 erly counties of the Lower Peninsula, near the cen- 

 ter-line of the State and so removed from the Lakes' 

 ameliorating influence, terminate their growing-sea- 

 son on the average at as early a date as Grand Marais 

 or the West Keweenaw shore some four hundred miles 

 to the north. Indeed, the lines passing through 

 points in the Lower Peninsula having the same nor- 

 mal date for the occurrence of the first killing frost 

 of autumn, very strikingly are north and south lines, 



